Many investigators today are dissatisfied with Hull's (1943) drive theory and favor an incentive theory of drive (e.g., Bolles, 1967). Yet little research has been done with the specific aim of developing a model of drive effects. One long-term aim of the proposed research is to develop such a model. In addition, the data currently available suggest that what expectations an animal has regarding goal events determine the effect drive variations will have on performance, and that drive variations may be critical in determining what emotional response an animal makes to goal events, and thus, perhaps, what expectancies are developed regarding goal events. Thus to understand how goal events are represented and how these representations affect performance it is necessary to manipulate drive. The experiments proposed involve variations in hunger, thirst, and food and water reward in instrumental learning situations involving rats. Further work would involve extensions to other drive-reward systems.